Detector system for detecting glowing particles

ABSTRACT

The present invention relates to a detector arrangement inlcuded in a preventative, protective system. The sensor lobes of at least two sensor units or sensor sections are arranged to cover the cross-sectional area of a tubular transport device. The arrangement includes a unit for evaluating the output signals of the sensor units, and an activation unit which is adapted to evaluate sensed sub-intensities relating to wavelength ranges and each deriving from said sensor units and to thus coordinate received wavelength-related and sub-intensity-dependent signals for calculating and establishing therefrom the relevant disposition of the particle to initiate fire and/or explosion or some other danger.

FIELD OF INVENTION

The present invention relates generally to a detector arrangement andmore specifically to a detector arrangement which is designed to detectin a stream of loose material the presence of one or more individualparticles that has/have a temperature and/or an energy content such asto be able to incite fire or cause an explosion to take place in adownstream particle or material collecting risk zone.

By loose material is meant any type of material that can be transportedby or in a gas mixture, normally air, wherewith the individual particlesof the loose material are normally spaced from one another.

Loose material of this kind may consist of very fine particles in thenature of dust, or may consist of powder particles or granularparticles. Wood chips, pellets, straw and like materials can also betransported in this way.

The inventive detector arrangement is adapted to be included in apreventative, protective system that includes one or more sensor units,an evaluation unit evaluating the output signals of said sensor units,and an activation unit connected to said evaluation unit, wherein atleast one individual particle that can be sensed by the sensor units andhaving an energy content determined in the evaluation unit as exceedinga predetermined value will cause the activation unit to switch from afirst state (a rest state) to a second state (an activating state).

More particularly, the detector arrangement can be adapted for use in aprocess in which loose, process material is produced in a first unit andtransported therefrom to a receiving, second unit, wherein treatment ofsaid material in said first unit may result in one or more particlesbeing heated to a temperature that is sufficiently high to initiate fireand/or an explosion in at least the second unit, and in whicharrangement the transport system required to transport the loosematerial between said first unit and said second unit includes astabilising zone or disturbance zone, a zone that indicates the presenceof high temperature particles, an effectuating zone, an extinguishingzone, and a downstream risk zone adjacent to or within said second unit.

The stabilisation zone is intended to allow particles that have a lowenergy content and do not constitute a fire risk or explosion riskwithin the downstream located zones, and particularly within the riskzone, to reduce their energy content and therewith prevent saidparticles being indicated as a hazard within the immediate downstreamindication zone.

The indication zone includes one or more sensor units which function toindicate the presence of one or more individual particles whose energycontent is liable to incite fire or some other damage should saidparticle or particles appear in the downstream zones and thenparticularly in the risk zone.

Each of the aforesaid sensor units can co-act with a unit whichevaluates the output signals of a sensor unit, and with an activationunit such that when the sensor units indicate the presence of such ahazardous particle, the activation unit will activate an extinguishingmeans associated with said extinguishing zone and/or a particle removalmeans.

The indication zone is followed by an effectuating zone whose length isadapted so that upon activation of means in said extinguishing zone saidmeans will have time to generate an extinguishing barrier before or asthe particle reaches said zone.

The extinguishing zone may also include a valve, which deflects acollection of material containing said particle from the transportationpath to the risk zone.

DESCRIPTION OF THE BACKGROUND ART

A preventative, protective system that includes one or more sensor unitsand associated detector arrangements of the aforedescribed kind ispreviously known and marketed by Firefly AB, Stockholm, Sweden. Thepreventative, protective system functions to indicate sparks andindividual, glowing particles in a stream of loose material, such asgranular material or dust, and to apply extinguishing means orsmothering means so as to prevent such glowing particles from reachingthe downstream process unit, such as a filter, a silo or the like, orfrom reaching the risk zone, which would otherwise be set on fire and/orcaused to explode.

The preventative, protective system utilises in operation variousdetector systems and detector arrangements for sensing and detectingindividual particles.

With regard to sensor units included in detector arrangements of theaforesaid kind and similar preventative applications, it has been foundthat they have a delayed reaction in industrial processes or are notsufficiently sensitive to be considered as an effective damage limitingmeans, which also applies to the output signal evaluating unit and theactivation unit.

Sensor units of this kind tend to react to individual particles that arenot harmful in certain circumstances, while in other circumstances theyfail to react to individual particles that can cause damage by fire orexplosion.

In this regard, it has been found necessary to maintain a safety rangethat is so large as to cause the equipment to react to particles thatcan cause no damage rather than not react to particles that are liableto cause damage, this being a preferred safety measure.

It is known to use temperature detectors in the present context,although experiences have shown in practice that these detectors oftenfail to react until a fire has already developed.

Although flame detectors used in the present context are sensitive tosmall (low) flames, their use in a preventative, protective system isexcluded because they react much too late.

It is also known to use pressure detectors that operate with highsensitivity and with small time constants, but also such detectorsnormally require an initial explosion or combustion in order to react.

It is also known to use wavelength-related detector arrangements.

Practical experiences, however, indicate that even discrete particlesthat radiate solely within one wavelength range, solely for thermalradiation in a transport path, having a temperature in the range of 400°C. are a fire and explosion risk in various process plants wherecombustible, finely divided and loose material is transported with theaid of a vehicle gas or vehicle gas mixture, preferably an air stream.

The contents of Patent Publication U.S. Pat. No. 5,193,622, whichdescribes a detector arrangement that includes a sensor unit, alsobelongs to the known prior art. Patent Publication SU-A1-1,729,528teaches a detector arrangement that includes several sensor units.

With respect to the features associated with the present invention, itcan be mentioned that Patent Publication U.S. Pat. No. 5,749,420describes a detector arrangement in which an indicating and activatingunit 12 is adapted to evaluate and sense the radiation intensity fromeach of a number of sensor units 105, 107.

With respect to the aforementioned publications, the sensor units usedare adapted to receive summated each wavelength-related radiationintensity from a large wavelength range or from the whole of thewavelength spectrum of the particle.

DISCLOSURE OF THE INVENTION Technical Problems

When taking into consideration the technical deliberations that a personskilled in this particular art must make in order to provide a solutionto one or more technical problems that he/she encounters, it will beseen that on the one hand it is necessary initially to realise themeasures and/or the sequence of measures that must be undertaken to thisend, and on the other hand to realise which means is/are required tosolve one or more of these problems, and on this basis, it will beevident that the technical problems listed below are highly relevant tothe development of the present invention.

With respect to the singularities associated with the present invention,it is necessary to realise that each individual, discrete particle ofloose particulate material carried in a transport system that has anelevated energy content will generate radiation that can spread within awide wavelength spectrum which may extend from the range of ultravioletradiation (UV radiation) to the infrared radiation or thermal radiationrange (IR radiation) via visible radiation, and that thermal radiationis of particular significance to the system in the case of manyapplications.

This wavelength spectrum or large wavelength range can also be dividedinto a number of narrow wavelength ranges.

When considering the present state of the art as described above, itwill be evident that a technical problem resides in creating with theaid of simple means a detector arrangement that is highly reliable andwith which the activation unit will take an activation mode solely whenthere is a real danger of fire or a corresponding hazard, and whichenables the safety range to be kept within narrow limits.

It will also be seen that a technical problem is one of realising thesignificance of establishing, usually empirically, an adapted, relevantlarge wavelength range within which the wavelength spectra of theparticles can be evaluated, with respect to every process plant andcombustible, finely divided loose material used therein.

Another technical problem is one of realising the significance ofestablishing for each process plant and the combustible, loose, finelydivided material used therein, a suitable number of narrow wavelengthranges and the width of the wavelength ranges located within the adaptedlarge wavelength range that is the subject of evaluation, said number ofnarrow wavelength ranges normally being established empirically.

It will also be seen that a technical problem is one of realising thesignificance of adapting the width of each of the selected number ofwavelength ranges in dependence on the process plant used and the loosematerial handled therein, so as to provide a high safety factor within anarrow safety range, and so that activation of relevant safety meanswill only take place in the event of real danger.

It will also be seen that a particularly technical problem is one ofenabling the total energy content of a single particle to be evaluatedwith the aid of simple means, by evaluating and signal-processing onlyrelevant intensity values that can be evaluated within chosen, limitednarrow wavelength ranges.

Another technical problem resides in the ability to approximate acomplete intensity curve for-a single particle with the aid of a fewmeasuring points, by choosing measuring points within a limited,relevant wavelength range.

Another technical problem is one of realising the significance of andthe advantages associated with establishing, normally empirically, foreach process plant and loose combustible material handled therein anadapted sub-intensity value for each evaluatable narrow wavelengthrange, so that the activation unit will be able to adopt an activationstate immediately when only one or a few of the sub-intensity valuessensed exceeds/exceed a corresponding, adapted and determinedsub-intensity value.

Another technical problem resides in choosing from among a total numberof available wavelength ranges a smaller number of narrow wavelengthranges which must indicate in respect of a single particle thesub-intensity values that correspond to or exceed established andadapted sub-intensity values so as to cause the activation unit to adoptan activation mode, this choice being made in respect of each processplant and the combustible material handled therein.

With regard to the known prior art as described above, the primary aimof the present invention is to provide an improved detector arrangementwhich is able to evaluate the energy content of loose, discreteparticles in the process plant in a more positive and more simplemanner, and also to be able to detect and indicate single particles thathave a temperature slightly below 400° C.

Another technical problem is one of realising the advantages that areafforded when at least two of the sensor units or sensor sections in theinventive detector arrangement have sensing lobes which cover thecross-section of a loose material transportation path, and to accuratelyestablish the energy content of an indicated single particle on thebasis of received signals related to a narrow wavelength range,regardless of the orientation of the particle in said cross-section andwhile taking the distance from respective detectors into account.

In this respect, a technical problem resides in creating with the aid ofsimple means a detector arrangement in which a first sensor unit orsection of said unit is able to sense, or detect, the sub-energy contentof a single particle present and the sub-intensity value within a firstnarrow wavelength range, and that a second sensor unit or sectionthereof is adapted to sense, or detect, the sub-energy content andsub-intensity value of said particle within a second narrow wavelengthrange, and that an evaluating unit is adapted to process the outputsignals from both said sensor units and accordingly either inhibitactuation of an activation unit to an activation mode or to cause saidactivation unit to switch to its activation mode.

Another technical problem is one of realising the significance of andthe advantages that are afforded by adapting a sensor unit to sense, ordetect, the sub-energy content of a particle within mutually separate,narrow wavelength ranges located within the full wavelength spectrum ofthe particle radiation with respective wavelength ranges having one andthe same width or mutually different widths.

Another technical problem is one of realising the significance of andthe advantages that are afforded when a plurality of sensor units orsensor sections are adapted to sense, or detect, the sub-energy contentof a particle and/or its sub-intensity within mutually overlappingwavelength ranges.

Another technical problem is one of realising the significance of andthe advantages that are afforded by allowing the evaluating unit tocompare the sub-intensity of a received output signal with a stored andmaximised wavelength range value, and to actuate the activation unit inthe event of the sub-intensity of an output signal exceeding saidmaximised value.

Another technical problem is one of realising the significance of andthe advantages that are afforded by enabling the evaluating unit tocompare the sub-intensities of a plurality of received output signalswith a plurality of stored, maximised wavelength range values and tocause the activation unit to switch to its activation mode when thesub-intensities of predetermined output signals and/or with apredetermined number of output signals exceed said maximised value.

Another technical problem is one of realising the significance of andthe advantages that are afforded by choosing said narrow wavelengthranges with a wavelength within the heat radiating range, such as awavelength greater than 1.0 μM.

Another technical problem is one of realising the significance of andthe advantages afforded by choosing a narrow wavelength range or narrowwavelength ranges that have a wavelength within 1.2 to 5.0 μM, such as1.4 to 3.5 μM.

Another technical problem is one of realising the significance of andthe advantages afforded by adapting the chosen narrow wavelength rangesand the maximised wavelength values related thereto in accordance withone or more of the following criteria: choice of material to betransported, material in anticipated particle presence, the design ofthe preventative, protective system, the process concerned, etc.

Another technical problem is one of realising the significance of andthe advantages afforded by adapting a sensor unit or sensor sections toevaluate the sub-energy content of a particle within at least three,preferably more, and, e.g., up to ten, different narrow wavelengthranges located within the full wavelength spectrum of the radiation.

It will also be seen that a technical problem is one of realising thesignificance of and the advantages afforded by adapting the evaluatingunit to evaluate a sensed, or detected, sub-intensity-dependentwavelength-related output signal deriving from a narrow wavelength rangefrom each of said sensor units or sensor sections, and to co-ordinatethe sub-intensity-dependent signals so as to be able to calculate andalso to establish the relevant energy content of the particle and itsdisposition to initiate fire and/or explosion in a downstream risk zone.

It will also be seen that a technical problem is one of realising thesignificance of arranging said sensor units or sensor sections, eachbeing allocated a narrow wavelength range, diametrically and/oruniformly around an inner peripheral surface of a tubular conduit ofcircular cross-section, and then to realise the significance of theorientation of the number of sensor units and/or sensor sections used.

It will also be seen that a technical problem resides in realising thesignificance of positioning the sensor units and/or the sensor sectionsopposite one another about an inner perimeter surface of a tubularconduit of angular cross-section and to realise the significance ofplacing the sensor units and/or the sensor sections in the corners ofsaid conduit.

Another technical problem is one of realising the significance ofcoordinating the sensor units symmetrically and diametrically oppositeone another around an inner peripheral surface of a tubular conduithaving a right-angled cross-section, and to realise for whichapplications said sensor units and/or said sensor sections shall beplaced in the corners of said conduit.

Another problem resides in realising the advantage of using a sensorunit and/or a sensor section that has a detection angle of about 180degrees and a sensing lobe that has a corresponding semi-circular shape.

Another technical problem is one of realising the significance ofcovering each sensor unit and/or its sensor section with a protectivecover that includes a plurality of mutually adjacent slots, said slotspreferably being orientated in a direction perpendicular to or generallyperpendicular to the feed direction of said material, and all of thesensor units and/or the sensor sections being co-ordinated around oneand the same cross-section plane through the transport paths.

Another technical problem is one of designing the sensor unit inaccordance with circumstances that prevail at a particular time, eitherby adapting a sensor unit to evaluate the sub-intensity values for aplurality, such as all, chosen narrow wavelength ranges, or by choosinga number of sensor units which are each adapted to evaluate thesub-intensity value of one narrow wavelength range or of a few narrowwavelength ranges.

Solution

With the intention of solving one or more of the aforesaid technicalproblems, there is provided in accordance with the present invention anarrangement which can be included beneficially in a preventative,protective system of the aforedescribed kind, said arrangement includinglight-sensitive and heat-sensitive devices in the form of a sensor unitand associated sensing circuits for detecting a single particle that hasa high energy content.

There is normally used in such a detector arrangement at least twosensor units or sensor sections whose sensing lobes are intended tocover a cross-section of the transportation path of loose particulatematerial.

The present invention relates particularly to a detector arrangementwhich can be adapted for inclusion in a preventative, protective systemand that includes a number of sensor units or sensor sections, a unitfor evaluating the output signals of said sensor units and an activationunit which is coupled to the evaluating unit, wherein sensing of atleast one individual particle whose energy content established in theevaluating unit is found to exceed a predetermined value is able toswitch the activation unit from a first state to a second state.

It is particularly proposed in accordance with the present inventionthat a first sensor unit or sensor section is adapted to sense thesub-energy content of said individual particle and/or its sub-intensityvalue within a first narrow wavelength range, that a second sensor unitor sensor section is adapted to sense the sub-energy content of the sameindividual particle and/or its sub-intensity value within a secondnarrow wavelength range, and that an evaluating unit is adapted to allowthe output signals from both sensor units or sensor sections to beprocessed and to inhibit actuation of the activating unit to itsactivating position or to cause said activation unit to switch to itsactivation state on the basis of the result.

By way of preferred embodiments that lie within the scope of the presentinvention, it is proposed that a plurality of sensor units or sensorsections are adapted to sense the sub-energy content of a particleand/or its sub-intensity value within a number of mutually separatenarrow wavelength ranges.

A plurality of sensor units or sensor sections may be adapted to sensethe sub-energy content of a particle within mutually overlappingwavelength ranges.

It is also proposed that the evaluating unit shall be adapted to allow acomparison to be made between the sub-intensity of a received outputsignal and a stored maximised wavelength range-related value and tocause the activation unit to switch to its activating mode when thesub-intensity of an output signal exceeds said maximised value.

The evaluating unit will preferably be adapted to compare the intensityof a plurality of received output signals with a plurality of storedmaximised values related to wavelength ranges and to cause theactivation unit to switch to its activating mode only when thesub-intensities of a predetermined number of output signals exceed saidmaximised values.

Each of the narrow wavelength ranges will preferably have a wavelengthgreater than 1.0 μM.

More specifically, said narrow wavelength ranges are chosen from withina selected large wavelength range, such as 1.2 to 5.0 μM.

The selected narrow wavelength ranges and the maximised values relatedthereto are adapted to one or more of the following criteria: the natureof the material being transported, the nature of the material in saidparticle, the design of the preventative, protective system, the processconcerned, etc.

It is also proposed that a sensor unit or a number of sensor sectionsare adapted to evaluate the energy content of an individual particlepresent and/or its intensity within at least three narrow wavelengthranges located within the total wavelength spectrum or a chosen largewavelength range with respect to the radiation emitted by an individualparticle.

It is also proposed in accordance with the invention that the evaluatingunit and the activation unit are adapted to evaluate a sensedwavelength-related sub-intensity from each of said sensor units orsensor sections, and to co-ordinate the received sub-intensity-dependentwavelength-related signals so as to be able to calculate and establishtherefrom the energy content or the like of said particle and therewithbe able to estimate the disposition of the particle to initiate relevantfire and/or explosion criteria in respect of a specific system and itsmaterial properties.

By way of proposed embodiments that lie within the scope of theinventive concept, it is proposed that said sensor units or sensorsections are disposed diametrically opposite one another or areuniformly spaced around the inner perimeter surface of a tubular conduitof circular cross-section.

It is also proposed that said sensor units or sensor sections aredisposed opposite one another around the inner perimeter surface of atubular conduit of angled cross-section, and to place said sensor unitsor sensor sections in the corners of said conduit.

The sensor units or sensor sections are disposed symmetrically and inmutually opposed relationship around the inner perimeter surface of atubular conduit of right-angled cross-section, and are preferably placedin the corners of said cross-section in respect of certain applications.

According to the invention, each sensor unit or sensor section has adetection angle of about 180 degrees.

It is particularly proposed that each sensor unit or sensor section canbe covered with a protective cover that includes a plurality of mutuallyadjacent slots that are orientated in a direction perpendicular to orsubstantially perpendicular to the feed direction of said material, andthat all sensor units or sensor sections are orientated in one and thesame plane or are at least orientated so that an individual particlepassing two or more sensor units or sensor sections can be evaluatedsimultaneously or generally simultaneously by all of said sensor unitsor sensor sections.

The invention also enables the use of one single sensor unit that isconstructed to evaluate all of the intensity values relating to thechosen narrow wavelength ranges, or a chosen number of sensor unitswhich are each adapted for evaluating the sub-intensity value of anarrow wavelength range or of a few narrow wavelength ranges.

Advantages

Those advantages that are primarily afforded by an inventive detectorarrangement and particularly when said arrangement is included in apreventative and protective system reside in the provision of conditionswhich enable two or more sensor units or sensor sections to evaluate thehigh energy content of individual, loose particles passing said sensorunits or sensor sections with greater precision than was earlierpossible regardless of the position of the particle within across-section of its path as a result of sensing such a particle in eachof the sensor units or sensor sections simultaneously with mutuallydiscrete and narrow wavelength ranges located within the wavelengthspectrum of the total radiation of the particle and by processing thesub-intensity signals generated by said single particle from each of thesensor units or sensor sections so as to enable the relevant energycontent of the particle to be established and to cause an activationunit to be brought to an activating mode when said energy contentexceeds a predetermined value.

In particular, a plurality of sensor units or sensor sections evaluatesub-intensities of the particle and on the basis of thesesub-intensities and a stored control value the relevant energy contentof the particle is evaluated and an activation circuit is activated whenthis evaluated value exceeds a predetermined value.

The main characteristic features of an inventive detector arrangementare set forth in the characterising clause of the accompanying claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of an inventive detector arrangement at present proposedand the application of such an arrangement in a preventative andprotective system will now be described in more detail with reference tothe accompanying drawings, in which

FIG. 1 is a block schematic illustrating generally a production processin which an inventive detector arrangement with accompanying evaluatingunit and activation unit is used;

FIG. 2 is a graph, which illustrates energy as a function of wavelengthand wherewith individual heat radiating particles having a temperatureof above 400° C. can be evaluated;

FIG. 3 is a cross-sectional view of a transport conduit in the form of athree-walled tubular part, with a sensor unit or sensor sectionpositioned in each corner;

FIG. 4 is a cross-sectional view of a circular transport conduit withfour sensor units or sensor sections positioned symmetrically therein;

FIG. 5 is a cross-sectional view of a square transport conduit and showsfour sensor units or sensor sections positioned at the corners of saidconduit;

FIG. 6 illustrates the principle of the present invention in evaluatingthe relevant energy content of a high temperature particle that passeseach of a number of sensor sections incorporated in a sensor unit;

FIG. 7 illustrates schematically the use of seven sensor sections forsensing the sub-intensity within a respective narrow wavelength rangewithin the total wavelength spectrum of a heat radiating particle, whereeach of said sensor sections is coupled to an output signal evaluatingunit and an activation unit;

FIG. 8 is a graph in which a maximum energy is given as the function ofthe wavelength and illustrates the division of the total wavelengthspectrum of a heat radiating particle in accordance with the invention;

FIG. 9 shows in sections A, B and C different co-ordinations of chosennarrow wavelength ranges within a chosen large wavelength range;

FIG. 10 illustrates an embodiment in which a number of sensor units,such as two sensor units, are coordinated for evaluating a respectivenarrow wavelength range;

FIG. 11 illustrates an embodiment in which a single sensor unit isadapted to evaluate a chosen number of narrow wavelength ranges, such asthree such ranges; and

FIG. 12 illustrates an embodiment in which a single sensor unit isadapted to evaluate a chosen number of narrow wavelength ranges, such asthree such ranges, through the medium of a filter element.

DESCRIPTION OF EMBODIMENTS AT PRESENT PROPOSED

FIG. 1 thus illustrates a preventative, protective system forapplication in a process, an industrial process, in which loose materialis produced in a first unit 1 and transported to a receiving, secondunit 2 through a transport system 3.

The invention is based on the concept that treated material, such asdisintegrated paper pulp, e.g. cellulose fluff, is fed into a mill 1 inthe direction of arrow 4 and transported to the second unit 2, in theform of a silo, with the aid of an air stream 6 and through the mediumof a conduit system 7, 8, 9 included in the transport system 3. Theexemplified disintegration of the paper pulp in the unit or mill 1 cancause one or more individual particles to be heated to a temperature ofsufficiently high magnitude to initiate a fire and/or an explosionwithin at least the second unit 2, and also within the transport system3.

Although the illustrated embodiment refers to the use of paper pulp thatshall be disintegrated and transported by an air stream to a silo, itwill be understood that the inventive concept can also be applied toother fields and also for other purposes and, in particular, for othermaterials.

The invention also requires all disintegrated particles to betransported as loose material by a gas or gas mixture, normally air.

In addition, the concept of the invention also requires the materialtreated to be of such nature that individual particles may well have aheat content or thermal energy content that can cause a fire in theconduit system or in the storage space, i.e. the so-called risk zone 2.

In accordance with the invention, transportation of the loose materialin the conduit 5 between said first unit 1 and said second unit 2 iseffected by a transport system 3 which includes, among other things, astabilising zone 7, a zone 8 which indicates the presence of particlesthat have high temperatures, and an extinguishing zone preceding a riskzone 2.

The temperature indicating zone 8 includes initially a plurality ofsensors 10 with one or more sensor units or sensor sections 10 a-10 gconstructed in accordance with the present invention, as evident fromthe following description.

The sensor units 10 a-10 g may be orientated in one and the same planetransversely of the conduit 8, as shown in FIGS. 3 to 5, although theymay alternatively be spaced apart at adapted distances along saidconduit.

The invention is described in the following with reference to a singlesensor unit 10 that includes a number of sensor sections 10 a-10 g.

The person skilled in this art will be aware of how the signal fromseveral sensor units shall be evaluated and of the time factors thatneed to be included for evaluating mutually spaced sensor-unit signals,and consequently this will not be described in detail.

A chosen number of sensor sections 10 a-10 g are able to co-act with asensor-section output signal evaluating unit 16 over a multi-wire line11, wherein the evaluating unit 16 is connected to or included in anactivating unit 12.

When one of the chosen number of sensor sections 10 a-10 g indicates thepresence of an excessively hot individual particle, the unit 12 willactivate a device 15 associated with the extinguishing zone 9 such as todeliver an extinguishing substance and/or to effect removal of theparticles.

According to the present invention, a wavelength range relatedsub-intensity dependent on respective sensor sections 10 a-10 g can beevaluated via the unit 16 included in the activating unit 12 and, withthe aid of a calculating circuit 17, can activate a selected dangeravoiding measure, said avoidance measure being one of several availablemeasures although being an indicated and suitable measure.

The aforesaid evaluated wavelength-related sub-intensity and the sum ofa plurality of such evaluated sub-intensities provides a positiveindication of the relevant energy content of a particle and its dangerpotential and can be used as the basis for a narrow safety range.

When danger is indicated, the measure activated may consist in thechoice of a device available among a plurality of devices, such as oneof the three illustrated devices 19, 20 and 21, in response to anactivation signal present on the lines 19 a, 20 a or 21 a.

Alternatively, one and the same device may be caused to be used to agreater or lesser extent, by modifying the signal on one of said lines.

The invention also proposes that the calculating circuit, or computingcircuit, 17, can be programmed so that the choice of an appropriateaction will depend on the nature of the process and can be introducedvia a circuit 25 connected to the activation unit 12.

One measure may, for instance, comprise the activation of a valve in theconduit section 9 so as to deflect a collection of material thatincludes said particles.

The sensor sections 10 a-10 g are placed at a distance from said firstunit such that loose particles of low energy contents will be able topass respective sensor sections without initiating activation of theunit 12 and therewith making a selection via the unit 18.

The measures activated may also consist of engaging an entirewater-based extinguishing system or solely parts of system, whereindifferent nozzles in said system can be actuated by means of signalsdelivered on the lines 19 a and 20 a.

A signal on the line 20 a will activate two solenoid valves so thatpressurised water in the water conducting system can be sprayed on thematerial under transportation.

A single, further solenoid valve is activated via the line 19 a.

The water system can be switched-off via a line not shown.

The calculation unit 17 is programmed to determine the safety measurethat shall be taken and also the duration of said measure.

The calculation unit 12 may also be programmed, via a circuit 26, totake into account internal process conditions, such as the nature of thematerial being handled, the time delay required in view of the speed atwhich material is being transported at that moment in time, said speedbeing evaluated by a sensor 10′ whose output signal is delivered to thecircuit 17 on a line 11 a.

The unit 12 may also be programmed to take into account the design ofthe extinguishing equipment and its method of operation, so that anextinguishing zone will be developed immediately upstream of the pointat which the hazardous particle enters said zone.

Reference is made to the contents of Patent Publication U.S. Pat. No.5,749,420 for a more detailed description of the general processaccording to FIG. 1.

The present invention is based on several fundamental assumptions thatare described in more detail below with reference to FIG. 2.

FIG. 2 illustrates a number of graphs relating to the energy content (E)of a number of particles as a function of wavelength (μM), wherein thetotal energy of respective particles constitutes the integral of thecurve concerned.

In the illustrated case, the wavelength (μM) is divided into a number ofwavelength sections where one wavelength section M1 illustrates UVlight, one wavelength section M2 illustrates visible light, and onewavelength section M3 illustrates IR light or thermal radiation, thislatter wavelength section M3 being particularly significant to theinvention.

In connection herewith, it can be assumed that a particle having a massand a temperature according to graph 202 has a total energy content thatcorresponds to the integral over the wavelength range of the curve 202.

It has been found that a heat content representative of certainwavelength ranges (0.8-1.3; 3.3 and higher) is not significant withrespect to determining the relevant energy content of the particle anddecisive in evaluating the liability of the particle to cause combustionor some other danger.

Accordingly, the invention is based on the assumption that solely awavelength range 80, which can be considered to be representative of therelevant energy content of the particle, shall be evaluated by dividingthis wavelength range into a number of narrower wavelength rangesgreater than two, and to sense the prevailing sub-intensity within eachselected wavelength range.

For a chosen system, the relevant energy content of each particle cannow be represented by a graph 210.

The graph 201 illustrates the wavelength-dependency of the energygenerated by an incandescent lamp (2000° C.), while the graphs 202-205illustrate the wavelength-dependency of the energy content of individualparticles heated to a temperature of 700, 600, 500 and 400° C.

Each individual particle that has an elevated energy content willgenerate radiation, which is distributed over a large wavelengthspectrum, such as a wavelength spectrum of from 0.8 to 5.0 μM withrespect to a particle according to the graph 202.

The graph 202, and also the remaining graphs, shall be understood todistribute the energy-dependent intensity for each wavelength section inrespect of a particle that has a given mass and that derives from agiven material and has a temperature of 700° C.

In the case of a corresponding particle of lower mass, the graph 202′will have essentially the same appearance but will be located slightlybeneath the graph 202.

In accordance with the present invention, there is established for agiven process and a given material a large or broad wavelength range 80,from 1.5-3.3 μM, within which very broad wavelength spectra of from 0.8to approximately 5.0 μM of the particle can be evaluated and relevantassessment of requisite criteria for avoiding danger can be assessed,said wavelength range 80 normally being determined empirically.

A number of narrow wavelength areas or sections 81-87 within the largeror broader wavelength range 80 are determined, normally empirically,said wavelength sections 81-87 being seven in number in the illustratedcase.

The width of each of these narrow wavelength areas 81-87 shall bemutually adapted so as to provide a high safety factor.

Thus, it lies within the scope of the invention to give the individualnarrow wavelength areas mutually different wavelength widths.

According to the invention, a sub-intensity value 81 a-87 a for eachevaluatable narrow wavelength area 81-87 can be determined, normallyempirically, so that the activation unit 12 will be able to take anactivating position, via the circuits 17 and 18, immediately thesub-intensity values sensed exceed respectively the establishedsub-intensity values.

The activation unit 12 that includes the output signal evaluating unit16 may also be adapted to choose from the total number of wavelengthranges 81-87 a smaller number of wavelength ranges for each processplant and for the combustible material used therein, wherewith thissmaller number of wavelength ranges necessarily indicating for one andthe same particle the sub-intensity values that correspond to or exceedthe determined sub-intensity values so as to bring the activation unit12 to an activating mode via the circuit 18.

It is of course also within the frame of the invention to use a sensorunit for each of the narrow wavelength ranges 81-87 and to adapt asensor unit to receive radiation solely within its designed wavelengthrange, as described in more detail below with reference to FIGS. 10, 11and 12.

This adaptation may be made with the aid of optical filters or byappropriate selection of material in the sensor surfaces.

The following description illustrates a sensor unit that is comprised ofseven sensor sections 10 a-10 g, one for each of said narrow wavelengthranges 81-87.

Respective maximum permitted sub-intensity values 81 a to 87 a for eachof the wavelength ranges 81 to 87 have been combined in a graph 210 inFIG. 2.

It will be apparent that the activation unit 12 is actuated and a choicemade via the circuit 18 for each sub-intensity value applicable to thegraph 202, since the current sub-intensity values represented in thegraph 202 and related to respective wavelength ranges 81 to 87 exceedthe corresponding sub-intensity values 81 a to 87 a represented in thegraph 210.

An indication for activation of the activation unit 12 is given for thewavelength sections 85 to 87 with respect to a particle having anintensity according to graph 203, whereas the wavelength sections 81 to84 lack such an activation indication.

The software in the evaluating unit 16 and in the computer circuit 17now determines whether the activation unit 12 shall actuate the circuit18 or not. This decision may depend on the difference between thesub-intensity values in respective graphs 203 and 210 and/or on anevaluation of the significance of respective wavelength ranges.

With respect to a particle having a mass and a temperature according tograph 204, only the wavelength section 87 will initiate activation, andthe evaluating unit 16 can then decide, in co-action with the computercircuit 17, not to allow the activation unit 12 to activate the circuit18.

It will be clearly apparent from the aforegoing that the distribution ofthe graph 210 along the wavelength range 80 of maximum relatedsub-intensity values can vary in accordance with set requirements.

For instance, the graph 210 may be different for different materialselections, and it will be understood that the structure andconfiguration shown in FIGS. 2 and 7 are merely examples.

FIG. 3 is a cross-sectional view of a symmetrical triangular conduit 18which embraces a stream of airborne particles, and in which sensor units101, 102 and 103 each comprising seven sensor sections are provided inthe corners of the triangle in the manner shown in FIG. 3.

FIG. 4 is a cross-sectional view of a circular conduit 8 that includessensor units 104, 105, 106 and 107 each comprising seven sensor sectionsthat are orientated symmetrically with relation to each other anddirectly opposite one another.

Alternatively, the conduit may include three sensor units or more thanthe illustrated four sensor units.

FIG. 5 is a cross-sectional view of a conduit 8 in which sensor units108, 109, 110 and 111 each comprising seven sensor sections are providedin the corners of the conduit.

In the case of the FIG. 5 embodiment, the sensor units may alternativelybe positioned centrally with a wide sensing lobe of 180 degrees inrespect of the sides 112, 113, 114 and 115 of said conduit. The positionof the sensors will depend on the application.

According to one embodiment of the present invention, each of the sensorunits, such as the sensor unit 104 in FIG. 6, is provided with a numberof slots 104 a to 104 g, e.g. seven slots, where each slot is orientatedin a plane perpendicular to the transport direction -P- and where eachslot is coordinated with a sensor section 10 a, 10 b . . . 10 g.

Thus, a first slot 104 a positioned upstream of the transport directionP is allocated a first plane 51, a respective second slot 104 b isallocated a second plane 52 that is parallel with the first plane, andso on up to plane 57.

FIG. 6 also illustrates how an individual particle having an elevatedtemperature according to graph 202 first passes a point (p1) in theplane 51 and thereby activate a pulse 10 a′ delivered to the plane 51and intended for the sensor section 10 a in the unit 104.

When the same particle then passes the next point (p2), there isobtained in a corresponding manner and to a corresponding degree asignal 10 b′ for the sensor section 10 b, via the sensor unit 104, andso on.

Thus, a particle that has a sufficiently high energy content will beable to indicate seven high sub-intensity related pulses, one withineach narrow wavelength range 81-87, as said particle passes through theplanes 51-57 in the conduit 8.

A specific calculation or computation is required to calculate andevaluate the result of the indications obtained from the various sensorsections 10 a-10 g, as described below.

In order to compensate to the best possible extent for the contingencywhen the light intensity and/or the intensity of thermal radiation froma particle decreases with the square of the distance from a sensor unitor sensor section and increases with the square of the distance to asensor unit or sensor sector, an adapted calculation will preferably bemade from the sub-intensity values obtained from a plurality of sensorunits orientated in mutually the same cross-sectional plane of theconduit section 8 and according to the application of the invention, onthe basis of signals received from each of corresponding sensor sections(10 a-10 g), so as to be able to determine the relevant energy contentof said particle at that moment in time.

It also lies within the possibilities afforded by the invention thatwhen a particle has passed a chosen number of planes, such as the planes51, 52 and 53, and each of these planes has indicated a sufficientlyhigh signal for activation of an extinguishing means belonging to theextinguishing zone and/or a particle removal means 19, 20, 21, suchactivation can be triggered after a given number of clear indications,for instance three indications.

As shown in FIG. 7, the present invention relates more particularly to adetector arrangement that can be included in a preventative protectivesystem, comprising a number of sensor units or sensor sections 10 a-10g, and a unit 16 for evaluating sensor-unit output signals and includedin an activation unit 12 having a calculating circuit or computercircuit 17.

In each case, the presence of a particle sensed normally by a pluralityof the sensor sections 10 a to 10 g and having an energy contentestablished in the evaluating unit 16 as exceeding a predetermined valuecan cause the activation unit 12 containing the circuits 17 and 18 toswitch from a first state to a second state.

A first sensor section 10 a is adapted to sense the sub-energy contentof the particle within a first narrow wavelength range 81. A secondsensor section 10 b is adapted to sense the sub-energy content of theparticle within a second, narrow wavelength range 82 and so on up to andincluding the sensor section 10 g.

A summation of the energy contents for each wavelength range 81-87 willgive a total sum that is smaller than the total energy content of theparticle while, nevertheless, containing sufficient information toconstitute a significant indication of the total energy content of theparticle and thus its disposition to initiate combustion, explosion orto present some other danger.

The chosen curve form 210 is thus very critically similar to thelocation of the wavelength range 80 along the wavelength axis, thenumber of wavelength sections and the wavelength width of saidwavelength sections.

The output signal evaluating unit 16 is adapted to process the outputsignals received from a number of the sensor sections 10 a-10 g or fromall said sensor sections and to inhibit actuation of the activation unit12 and the circuit 18 or to initiate activation of said unit and saidcircuit on the basis of the result obtained.

Thus, a number of sensor sections 10 a-10 g shall be adapted to sensethe relevant energy content of a particle within mutually separate,narrow wavelength ranges 81-87 and 81′-87′ respectively (see FIGS. 9A to9B).

A number of sensor sections 10 a-10 g shall also be capable of sensingthe relevant energy content of a particle within mutually overlappingwavelength ranges, where the wavelength ranges 88 and 89 are overlappedby the wavelength range 88′ (see FIG. 9C).

The evaluating unit 16 according to FIG. 7 is also designed to comparethe sub-intensity 10 a′,10 b′ to 10 g′ of each received output signalwith a stored maximum value 81 a, 82 a to 87 a relating to saidwavelength ranges, and to send a signal which solely and clearlyindicates the signal structure when the sub-intensity of an outputsignal exceeds said maximised value 81 a, 82 a to 87 a; maximised value81 a smaller than the signal value 10 a; or sends to the calculatingcircuit 17 a signal that indicates the difference value (10 a′-81 a).

The evaluating unit 16 according to FIG. 7 is thus designed to comparethe sub-intensities of a plurality of received output signals 10 a′-10g′ with a plurality of previously stored maximised values 81 a to 81 grelating to wavelength ranges.

In a first embodiment, it is required that all output signals 10 a′-10g′ from the sensor sections 10 a to 10 g shall be higher than thosesignificant to the stored values 81 a-81 g corresponding to the graph210, in order for the calculating circuit 17 to send a signal to thecircuit 18.

In a second embodiment, it may be required that a chosen predeterminednumber of output signals whose respective sub-intensities exceed saidmaximised value are at least required for causing the calculatingcircuit 17 to send a signal to the circuit 18.

FIG. 7 is intended to indicate by way of example that the sensorsections 10 a, 10 c, 10 d and 10 e alone shall indicate, via theiroutput signals 10 a′, 10 b′. . . 10 g′, an excessively high, relativeenergy content for actuation of the circuit 18 via a calculating circuit17 included in a function block 17.

The signal 10 a′ is compared with the value 81 a in a comparison circuit71, and a signal indicating an excessively high value is sent on line 71a when the value of the signal exceeds the stored value.

The comparison circuit 71 may be modified so that the signal transmittedon the line 71 a will correspond to the evaluated difference value.

In this latter application, it may be convenient to evaluate themagnitude of the difference values, such as values 10 a′-81 a, via acircuit 17′, and to initiate activation of the circuit 18 only in theevent of a value that exceeds a determined limit value.

It is also possible to weight the values, such as values 10 a′-81 a, andtherewith allot greater significance to certain values within moremeaningful wavelength ranges than others.

The wide wavelength range intended for evaluation purposes is chosenwith a wavelength that exceeds 1.0 μM and lies within the UV range orthe heat radiating range M3, specifically, said wavelength range ischosen with a wavelength within 1.2 to 5.0 μM, such as 1.4 to 4.0 μM.

The chosen, narrow wavelength ranges and the maximised wavelengthrange-related values 81 a, 82 a to 87 a related to said narrowwavelength ranges are adapted to one or more of the following criteria:the material to be transported, the vehicle gas used, the anticipatedmaterial in the individual particle present, the design of thepreventative, protective system, the process concerned, etc.

A sensor unit 10 including sensor sections such as sections 10 a-10 g isadapted to evaluate the relevant energy content of an individualparticle by using to this end only a few narrow wavelength ranges, suchas from three to ten such ranges.

The design of the sensor unit 104 is such that conditions exist within acasing for evaluating the sub-intensity value of discrete, narrowwavelength ranges 81 to 87 in the integrated sensor sections 10 a to 10g.

As evident from FIG. 10, an optical filter and a related sensor unit 10a, 10 b . . . 10 g may be used for each narrow wavelength range.

Beams or rays within the wavelength spectrum of the particle and atleast within the wavelength range 80 radiate in onto an optical filter90 a which allows beams or rays within the wavelength range 81 to passthrough to a sensor unit 10 a. Beams or rays within the wavelength range80 radiate in onto an optical filter 90 b which allows radiation in thewavelength range 82 to pass to a sensor unit 10 b, and so on.

The signals carried on the lines 11 b, 11 c . . . 11 g are coordinatedin the calculating circuit 16 and compared with the stored values 81 a,82 a . . . 87 a.

FIG. 11 illustrates an embodiment where the wavelength spectrum of theparticle and at least the large wavelength range 80 radiates in towardsa number of optical filters 90 a, 90 b and 90 c, three such filters inthe illustrated case, which allow radiation in the wavelength ranges 81,82 and 83 to pass to a common sensor unit 10 k which receives thesesub-intensities and co-ordinates the same by summation to the calculatedunit 16, via a line 11 k.

FIG. 12 illustrates a combined optical filter 90 m which is providedwith a number filter sections 90 n, 90 o and 90 p, in the illustratedcase three, where each filter section is adapted to allow a narrow,wavelength range 81, 82 and 83 to pass concentrated to a sensor unit 10k, according to FIG. 11.

It will be obvious from this that safer detection is achieved whenapplying the conditions required to indicate fire danger or some otherdanger from values that are only slightly beneath the lowest ignitiontemperature of the loose material and its concentration.

It will be understood that the invention is not restricted to thedescribed and illustrated exemplifying embodiment thereof and thatmodifications can be made within the scope of the inventive concept asillustrated in the accompanying claims.

What is claimed is:
 1. A detector arrangement adapted for use in apreventative, protective system and comprising a number of sensor unitsor sensor sections, a sensor-unit output signal evaluating unit, and anactivation unit which co-acts with said evaluating unit, wherein atleast one particle whose presence is sensed by the sensor units and thathas an energy content determined by the evaluating unit that exceeds apredetermined value causes the activation unit to switch from a firststate to a second state, wherein a first sensor unit or sensor sectionis adapted to sense the sub-energy content of a particle and/or thewavelength intensity of said particle within a first wavelength range;in that a second sensor unit or sensor section is adapted to sense thesub-energy content of the same particle and/or its wavelength intensitywithin a second wavelength range; and in that the evaluating unit isadapted to allow the output signals from the sensor units or the sensorsections to be processed and in that activation of the activation unitis either inhibited or initiated on the basis of the result obtained,wherein the plurality of sensor units or sensor sections are adapted tosense the sub-energy content of a particle and/or its wavelengthintensity within mutually discrete wavelength ranges, and wherein theevaluating unit is adapted to allow the sub-intensity of a receivedoutput signal to be compared with a stored maximizedwavelength-range-related value and to allow actuation of the activationunit at least when the sub-intensity of an output signal exceeds saidmaximized value.
 2. A detector arrangement according to claim 1, whereina plurality of sensor units or sensor sections are adapted to sense thesub-energy content of a particle and/or its wavelength intensity withinmutually overlapping wavelength ranges.
 3. A detector arrangementaccording to claim 1, wherein the evaluating unit is adapted to allowthe sub-intensities of a plurality of received output signals to becompared with a plurality of stored maximized wavelength-range relatedvalues and to actuate said activation unit in the event of apredetermined number of output signals whose respective sub-intensitiesexceed said maximized value.
 4. A detector arrangement according toclaim 1, wherein each of said wavelength regions has a wavelengthexceeding 1.0 μM.
 5. A detector arrangement according to claim 4,wherein each of said wavelength ranges has a wavelength within 1.2 to5.0 μM, such as 1.4 to 4.0 μM.
 6. A detector arrangement according toclaim 1, wherein the selected wavelength ranges and maximized wavelengthranges related thereto and the related sub-intensity values are adaptedto one or more of the following criteria: the nature of the material insaid particle, the design of the preventative, protective system, theprocess concerned, etc.
 7. A detector arrangement according to claim 1,wherein a sensor unit is adapted for evaluation of the sub-energycontent of a particle and/or its wavelength intensity within at leastthree wavelength ranges.
 8. A detector arrangement according to claim 1,wherein a number of sensor sections within a sensor unit.
 9. A detectorarrangement according to claim 1, wherein each sensor unit included in aplurality of sensor units co-acts with a respective optical filter. 10.A detector arrangement according to claim 1, wherein a sensor unitco-acts with a selected number of optical filters.
 11. A detectorarrangement according to claim 1, wherein a sensor unit co-acts with anoptical filter adapted for a plurality of wavelength ranges.
 12. Adetector arrangement according to claim 1, wherein the sub-energy valuesof a number of sensor units or sensor sections are coordinated andadapted to include solely the relevant energy content of a particle. 13.A detector arrangement adapted for use in a preventative, protectivesystem and comprising a number of sensor units or sensor sections, asensor-unit output signal evaluating unit, and an activation unit whichco-acts with said evaluating unit, wherein at least one particle whosepresence is sensed by the sensor units and that has an energy contentdetermined by the evaluating unit that exceeds a predetermined valuecauses the activation unit to switch from a first state to a secondstate, wherein a first sensor unit or sensor section is adapted to sensethe sub-energy content of a particle and/or the wavelength intensity ofsaid particle within a first wavelength range; in that a second sensorunit or sensor section is adapted to sense the sub-energy content of thesame particle and/or its wavelength intensity within a second wavelengthrange; and in that the evaluating unit is adapted to allow the outputsignals from the sensor units or the sensor sections to be processed andin that activation of the activation unit is either inhibited orinitiated on the basis of the result obtained, a first unit forproducing loose material and a second unit for receiving the loosematerial from the first unit, wherein said first unit imparts to one ormore of said individual particles a temperature and/or an energy contentthat is sufficiently high to initiate fire and/or explosion in at leastthe second unit, wherein a transportation path of the loose materialbetween said first unit and said second unit including a stabilizingzone, a high particle temperature indicating zone and an extinguishingzone, said indicating zone including a plurality of sensor units orsensor sections adapted to sense the energy content of and/orwavelength-related intensities of said particles, wherein said sensorunits or sensor sections are able to co-act with a sensor-unit outputsignal evaluating unit and an activation unit so that when at least oneof the sensor units or sensor sections generates an indication of thepresence of a particle that has a high energy content there is activatedan extinguishing means belonging to said extinguishing zone and/orparticle removal means, and wherein the sensing lobes of at least twosensor units or sensor sections are intended to cover a cross-sectionalarea of the loose material transportation path, wherein said evaluatingunit is adapted to sense and to evaluate each sub-intensity-dependentsignal related to a narrow wavelength range from each of a number ofsensor units or sensor sections, and an evaluating unit is adapted tocoordinate, the thus received sub-intensity-dependent signals related tosaid wavelength range for calculating and establishing the relevantdisposition of a chosen particle to initiate fire and/or explosion or tocreate some other hazard.
 14. A detector arrangement according to claim13, wherein each of said sensor units or sensor sections is allocated anarrow wavelength range and in that said units or sections are disposeddiametrically or uniformly around the inner peripheral surface of aconduit of circular cross-section.
 15. A detector arrangement accordingto claim 13, wherein said sensor units or sensor sections are disposedopposite one another about the inner perimeter surface of a tubularconduit of angular, cornered cross-sectional shape.
 16. A detectorarrangement according to claim 13, wherein said sensor units or sensorsections are disposed symmetrically and opposite one another about theinner perimeter surface of a tubular conduit of right-angledcross-sectional shape.
 17. A detector arrangement according to claim 13,wherein each sensor unit or sensor section is allocated a detectionangle of about 180 degrees.
 18. A detector arrangement according toclaim 13, wherein each sensor unit or sensor section is covered by aprotective element that includes a plurality of mutually adjacent slotsthat are orientated in a direction perpendicular to, or essentiallyperpendicular to, the feed direction of said loose material.
 19. Adetector arrangement responsive to the energy content of particlesflowing in a flow path for actuating ignition suppression meansoperative in response to an activation signal to prevent ignition of theparticles in the flow path, each individual particle having a senseableenergy content, comprising: a plurality of sensor locations in the flowpath, the sensing locations being selectively responsive to the energycontent of the particles in a defined relatively narrow energy band foreach sensor location, each sensor location for producing a sensor outputcorresponding to the level of energy of a particle in the flow path atthe sensor location that lies within the defined energy band for thesensor location; a evaluating unit responsive to the sensor outputs forproducing an output when at least one selected sensor output exceeds aselected value; an activation unit responsive to the output of theevaluating unit for producing the activation signal for communication tothe ignition suppression means.